In certain bearing applications of large size, it is desirable to support a tubular shaft having as large an inner opening as possible, i.e., a shaft having as small a material thickness as possible. This is desirable in the context of, for example, dewatering rolls in the paper and pulp making industry where it is desirable to suck water by means of a vacuum or by drainage from a wire part into the roll and to lead away the water through a tubular shaft journal connected to the roll. To obtain the biggest possible suction capacity, it is advantageous to utilize as big an internal tube diameter as possible. At the same time, from the standpoint of space and weight, it is desirable to avoid increasing the external diameter of the tubular shaft more than what is absolutely necessary.
Conventional applications, therefore, have used a tubular shaft having as thin a wall as possible taking into consideration the expected loads and stresses. On this shaft the inner race ring of the bearing is mounted on a taper sleeve or by heating the inner race ring or driving it up the shaft by aid of pressure oil. Due to the large dimensions of the inner race ring, such heating can hardly be effected in an oil bath, with electrical resistance heating or with other rational methods. Rather, the heating must be carried out manually with a gas torch or the like, i.e., in a rather non-rational manner. Driving or moving up the bearing inner race ring on a tubular taper shaft or on a taper adapter sleeve also involves other difficulties, not the least of which involves the large dimensions and the large weight of the components. Another big problem is of course when such bearings have to be exchanged. Here, the dismounting often may lead to deformation of the tubular, thin-walled shaft journal. A further serious problem with such bearing assemblies is that the bearing ring mounted on the tubular shaft has a tendency to come loose after an unacceptably short operation time. This results from the fact that the thin-walled, tubular shaft is subjected to deformation depending on the stresses to which the bearing assembly is subjected under operation.
Other applications where bearing assemblies of this type are employed include mills, tubular stone crushers and the like. In the case of tubular stone crushers, it is desirable to be able to feed stone lumps having dimensions as large as possible through the tubular shaft journal of the crusher casing. In such applications, the bearing assembly is generally subjected to bigger stresses, which further increase the risk for shaft deformation and early bearing failure.
Generally, the bearing assembly might be advantageous for all types of rotary drums where the sole purpose for the drum shaft is to constitute a seat for the bearing.